Stencils have been used for a long period of time and there are a large number of patents which attest the development of different types of improved stencils and techniques for using the same. Thus, for example, the development of stencilling apparatus may be attested by U.S. Pat. Nos. 52,234; 159,725; 932,867; 1,600,177; and 4,319,524.
In U.S. Pat. No. 52,234, which was granted Jan. 23, 1866, J. Wentz shows a simple track arrangement into which are inserted plates which are perforated to bear intelligence so that a grouping of figures or letters can be readily arranged in a holder with the joints of the plates being perfectly formed and overlapping so that there is no possibility of paint working between the plates during a marking operation.
In U.S. Pat. No. 159,725, G. E. Warren also shows a stencilling arrangement wherein tracks or grooves are provided for accommodating plates bearing intelligence. These plates are held in position by the utilization of nuts and bolts cooperating with a clamping arrangement whereby the plates ae prevented from shifting in position.
A more complicated stencilling apparatus appears in U.S. Pat. No. 932,867 wherein O. James shows a stencilling apparatus formed in the manner of a book comprising hinged elements. In one of these elements are provided slots through which arrangements of plates are exposed. These plates are held in position by spring-loaded wires or rods which press against the plates. The plates are otherwise held in position by incorporating projections which are accomodated in notches.
A. Hurewitz shows in U.S. Pat. No. 1,600,177 an arrangement whereby tracks or grooves are formed for receiving letter plates therein. The base element in which the tracks are formed comprises a laminar arrangement of sheets which are bound together by the projection of ears through appropriately provided slits whereby a multi-layer base element is formed in which the plates are selectively accommodated.
Developments have continued until recently as exemplified by U.S. Pat. No. 4,319,524 in which P. Dunham discloses a holder for the mounting of a plurality of stencil elements which may be readily changed. The stencil elements are provided in the form of bridges which are accommodated in notches or slots whereat they are held in position by overlying backing plates which are dimensioned to fit snugly into a recess and which are provided with apertures which register with the apertures provided in the base element.